Defining parthood in terms of life

A couple of days ago I blogged that van Inwagen is right that we should not expect an answer to the General Composition Question.

Now I am not so sure. Suppose van Inwagen is right about the Special Composition Question having the answer he thinks it has: Necessarily, the xs compose another thing if and only thing they have a life together.

The following is then plausibly true:

1. Necessarily, y is a part of z if and only if y = z or there is a life L and xs such that (a) the xs live life L together, (b) z itself lives life L, and (c) y is among the xs.

But if so, then we have a non-mereological definition of parthood, and if substitute that into the definition of composition, we get a non-mereological account of when the xs compose y.

Maybe the problem with (1) is that it commits one to an ontology that quantifies over lives (which are presumably some kind of event), rather than just having some plural predicate like “are jointly lifewise active”.

But one can perhaps escape even that. Perhaps we can suppose a plural predicate S(xx,yy) which expresses the idea that the xx’s same-co-living. One might want to paraphrase that as “the xx live the same life as the yy do”, but that would commit one to quantifying over lives. And then we can say:

2. Necessarily, y is a part of z if and only if y = z or there are xx that have y among them such that L(xx,z).